Alien worlds share little in common with our planet, new study suggests

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This artist’s impression shows the super-Earth exoplanet GJ 1214b passing in front of its faint red parent star. The exoplanet, orbiting a small star only 40 light-years away from us, has a mass about six times that of the Earth. GJ 1214b appears to be surrounded by an atmosphere that is either dominated by steam or blanketed by thick clouds or hazes.

So-called "super-Earth" alien worlds may bear little resemblance to our own home planet and thus could be less likely to support life than previously believed, a new study suggests.

Super-Earths — alien planets bigger than Earth, but containing less than 10 times its mass — may be undifferentiated hunks of rock, possessing neither a mantle nor a core, researchers found. Super-Earths may also lack magnetic fields, which help protect life on our planet by shielding it from harmful radiation.

The scientists modeled the thermal evolution of rocky super-Earths, whose internal pressures are many times greater than those found in Earth's interior. Such high pressures lead to large viscosities and high melting temperatures, the team discovered — and these characteristics can have negative influences on a planet's habitability.

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For example, the team's calculations suggest that super-Earths may not be separated into a rocky mantle and metallic core like our planet is. [ The Strangest Alien Planets ]

“Current understanding is that the terrestrial planets in our solar system formed rapidly — in about the first 50 million years," Vlada Stamenkovic, of the Massachusetts Institute of Technology, said in a statement.

"The timescale of core formation depends strongly on viscosity," Stamenkovic added. "The high melting temperatures and the large viscosities that we’ve calculated for super-Earths suggest either a slow core formation or no core formation at all."

Earth's magnetic field is driven by the action of our planet's liquid metallic core. So if super-Earths lack such a core, they may lack magnetic fields as well, Stamenkovic said.

Even if rocky super-Earths are differentiated, convection would likely be sluggish, or stagnant layers could form deep in the mantle, researchers said. Either of these factors would reduce heat flow from the core and quash dynamo action that could generate a magnetic field.

The new study also found that the propensity for plate tectonics — which are a boon for life on Earth, helping to bring vital nutrients up from the planet's interior — decrease as a planet's mass increases. But water in a planet's crust can buffer this effect, so researchers can't say with confidence how likely super-Earths are to host plate tectonics.

Volcanic activity has also been vital to life on our planet, helping to establish Earth's atmosphere. The new research finds that the duration of volcanic outgassing generally decreases with increasing planetary mass, which could be more bad news for the prospect of life on super-Earths.

The new study also highlights how much is unknown about super-Earths, and the necessity of gathering more information about these mysterious worlds, researchers said.

"We will only be able to fully answer questions by gathering more data from high-pressure experiments and from spectroscopic observations of super-Earth atmospheres orbiting close-by bright stars," Stamenkovic said. "Theory shows the possibilities, which are far larger than previously thought, but remains full of uncertainties."

Stamenkovic will present the results at the European Planetary Science Congress in Madrid on Wednesday.

Southern stargazing

Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them.
(Y. Beletsky / ESO)
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A balloon's view

Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich.
(Kyle Moroney / AP)
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Spacemen at work

Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment.
(NASA)
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Special delivery

The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps.
(NASA)
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Accidental art

A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288.
(NASA / ESA)
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Supersonic test flight

A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

Red lagoon

The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes.
(ESO/VPHAS team)
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Fire on the mountain

This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people.
(NASA via AP)
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Where stars are born

An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues.
(NASA / JPL-Caltech)
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A long, long time ago...

This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang.
(NASA / NASA via AFP - Getty Images)
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Frosty halo

Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.